It may seem crazy, but in some clinical trials volunteers are purposely infected with diseases like the flu, cholera and malaria. These types of trials are referred to as challenge studies.
Recent news of a SARS-CoV-2 challenge study set to begin in early 2021 has been met with widespread disbelief. The study will be conducted in the United Kingdom, which has led the world in respiratory infection challenge studies.
Much can be learned from infections that occur in a controlled manner. In real life, it's usually unknown when a person was exposed to the infectious agent. In challenge studies, laboratory samples can be collected from the time of exposure, providing a wealth of information about the nature of early infection and immune response.
Additionally, challenge studies allow for the rapid assessment as to whether vaccines or treatments work as there's no need to wait for natural exposures to occur by chance.
In the UK study, healthy volunteers 20 to 30 years of age will have SARS-CoV-2 sprayed into their noses. The first volunteers will be used to figure out the dose required to cause an infection. Once the infective dose is known, the next set of volunteers will be used to see if vaccines can prevent infection and illness.
All clinical trials require approval by an ethics board. Ethics boards require that the risks to volunteers be minimized as much as reasonably possible. The UK volunteers are young adults and are therefore at low risk of death. This danger has been estimated to be similar to the annual risk of dying in a motor vehicle accident. To further reduce risk, volunteers will be immediately treated with remdesivir if SARS-CoV-2 is detected in the volunteer. Remdesivir is a proven treatment for SARS-CoV-2 and given early is hoped to prevent serious illness.
Critics argue that death isn't the only risk. SARS-CoV-2 is known to damage major organs, cause dangerous blood clots and result in months of fatigue and “brain fog.” Again, these adverse effects are much rarer in young adults. In truth, all clinical trials, not just challenge studies, carry risks.
Ethics boards require that volunteers fully understand the risks. Extra effort is put into ensuring volunteers understand the risk in challenge studies. No one questions that adults can chose to participate in risky activities such as hang gliding and mountain climbing. Likewise, adults select professions, such as law enforcement, which are riskier than participation in this challenge study.
Another argument is the study is unnecessary, and therefore doesn't justify the risk. The argument follows that treatments have improved, and vaccines are on the way. In reality, better treatments are needed, and we may require even better vaccines.
It may become difficult to perform large-scale, phase 3 trials like we've been doing if much of the population has been infected or already vaccinated. Challenge studies are a cost-effective method that can help speed up clinical development. They can play an important role in combatting SARS-CoV-2.
Vaccine Smarts is written by Sealy Institute for Vaccine Sciences faculty members Drs. Megan Berman, an associate professor of internal medicine, and Richard Rupp, a professor of pediatrics at the University of Texas Medical Branch. For questions about vaccines, email email@example.com.